Current vehicles, such as fork lift trucks, offer a combination of performance characteristics such as speed and maneuverability. These performance characteristics may be combined by an untrained, careless or reckless operator to cause excessive side moment of the vehicle. Excessive side moments can cause side overturn of the lift truck and other current vehicles. High travel speed is desirable for long, straight runs and a small turning radius is desirable for maneuvering in confined areas, such as narrow warehouse isles which are used to optimize warehouse space. Improper operation of a lift truck or other vehicle under extreme conditions such as a sharp turn at a high speed, may cause a side overturn. This is particularly true where the vehicle is equipped with highly responsive power steering. It is wasteful to limit vehicle speed owing to the fact that lower speed results in lower productivity and increased cost of operation. It is also undesirable to limit vehicle maneuverability.
The present invention is directed to overcoming one or more of the problems as set forth above.
According to the present invention, steering override apparatus is provided for a vehicle which has a steering axle assembly movable between a first position at which the turning radius in a first direction of the vehicle is at a preselected minimum value, a second position at which the turning radius of said vehicle is infinite, and a third position at which the turning radius in a second direction of the vehicle is at a preselected minimum value. The apparatus controls the turning radius of the vehicle in response to a predetermined operational rate by automatically limiting the movement of the steering axle assembly.